Method for improving synthetic hydrocarbon oils



Patented June 13, 1939 METHOD -FOR. IMPROYING SYNTHETIC HYDROCARBON OILSJoshua A. Tilton and Roger W. Richardson, Baton Rouge, La., assignors toStandard Oil Development'Company, a corporation of Delaware No Drawing.Application January '2, 1936,

' Serial No. 57,246

3 Claims.

This invention relates to a method for improving synthetic hydrocarbonoils by subjecting such oils to silent electric discharge. It relatesmore particularly to the refining of crude syn- 5 thetic oils,especially those having the property of decreasing the pour point ofwaxy oils when added thereto in small amounts. Such oils areconveniently described as pour point depressants.

The treatment of petroleum oils by silent elecl" tric discharge, orvoltolization, to increase their viscosity, has already been suggested.Such treatment may be conducted in any suitable ap ratus for bringingthe oil in contact with a silent electric discharge. It is conveniently5 conducted in a Siemens ozonization tube or in a trommel typevoltolizer, in which a thin film 01 oil is continuously passed betweenelectrodes in a reaction chamber maintained under an absolutepres-ure'ot about 2 to or cm. of mercury,

20 with an electric potential of about 1,000 to 10,000

volts or more at a frequency 01' about 500 to 10,000

cycles per second, the potential and pressure and space betweenelectrodes being adjusted so as'to obtain continuous silent electricdischarge.

It has how been foundthat the synthetic hydrocarbon'oil pour pointdepressants are greatly improved by submitting such oils, to treatmentwith the silent electric discharge. By this treatment highly refinedsynthetic oils may be obtained directly from the crude syntheticreaction productswithout the necessity of other renow commonly used.Such prod- .ucts are-also obtained in greater yields since the processof .the present invention is attended by none of the lgiises .1 0 lowquality or objectionable by-pr'oducts such as accompany ordinarytreating and refining methods.

When synthetic oils are subjected to relatively intensive treatment withsilent electric discharge,

40 the molecular weight and viscosity of the oils are increased severaltold, and products of high molecular weight of the order of-1,000 to2,000 more, and'o! high viscodties of the order oi 500 to.1,000 or moreseconds Saybolt at 210" F., are

obtained. Such products are especially suited for use as blending agentswith lubricating oils in order to produce blends of higher viscosity andviscosity index, and are suitably used in proportions of 5, 10, 20 to ormore with 50 lubricating oils, such as ordinary petroleum. lu-

bricating oils. Small amounts of these voltolized syntheticoils of theorder of 1, 5 to 10% may 'also be used as. oxidation inhibitors inlubricating oil blends, particularly with lubricating oils having highrates of oxidation, such as petroleum lubricating oils which have beenextensively r'efined with fuming sulfuric acid or by other refiningmethods adapted to increasesubstantially the viscosity index of the oil.

This invention comprises subjecting the syn-. thetic oils to a mildtreatment with silent electric discharge whereby any increase inviscosity Q! ,molecular weight of the oils is relatively small and theseare preferably not more than doubled. The increase in viscosity isgenerally not more than 10 to 50 or By this modification theobjectionable qualities of the impurities normally present in such oilsare greatly decreased or eliminated and many properties of the syntheticoils are greatly improved, such as color, cast, solubility and otherspecial properties. For example,

. the effectiveness of synthetic pour inhibitors is increased by thistreatment to an aptimum extent when the increase in viscosity by theaction of silent electric discharge is about 100% but less than 200% andpreferably less than about Other and further objects of this inventionwill be apparent from the resent description and the claims.

The property of certain types of condensatio products of decreasing thepour point (or solidification point) of waxy lubricating oils when,added thereto in small amounts is well known. Such condensationproducts are known as pour point depressants or "pour inhibitors. Theseproducts are usually viscous oils. They are described more fully in U.S. Patent No. 1,815,022 granted July 14, 1931, to G. H. B. Davis.Examples of such oils include alkyl-aryl condensation" .products whichare preferably prepared by condensation of aliphatic reagents having astraight carbon chain of 10 t6 30 or more carbon atoms with aromaticreagents containing condensed nuclei. An example 01' this type ofcondensation product is the viscous oil obtained by condensingchlorinated parafliruwax with naphthalenes by the Friedel-Craftsreaction, in the presence of a catalyst of the type of aluminumchloride.

It has now been discovered that the properties of such pour depressantsare markedly'improved by subjecting the condensation products to theaction of a silent electric discharge. This treatment is preferablyniild, as described above under The following examples are presented toillustrate one method for conducting this modificatnm of this invention,but are not to be construed as limiting the-invention in any way.

Example I ride to a solution of the reagents in kerosene at roomtemperature. The reaction mixture was then washed with aqueous causticsoda to neutralize any residual aluminum chloride, and the aqueous layercontaining the aluminous sludge charge in the was settled and separatelydrawn off. The oil layer was then distilled to remove the kerosene andany unreacted paraflin there was obtained as residue a viscous synthetichydrocarbon oil condensation product. This product, dissolved inkerosene, was agitated with a decolorizing clay, which was filtered oiland the kerosene again removed by distillation. There was thus obtainedas distillation residue an oil having a Saybolt viscosity of 297 secondsat 210 F. and a black, almost opaque color.

This condensation product was then subjected to the action ofsrllent'electric discharge in a Siemens ozonization tube at a pressureof '2 cm. of mercury absolute, using an electric potential of 2,000 to2,500 volts at 10,000 cycles per second. The apparatus was a verticalannular glass tube with concentric electrodes on both outside walls.Hydrogen was bubbled through the oil to maintain it in a state of foam.The treatment was continued for about 5 hours in order to secure anincrease in viscosity of about 100%.

The resulting product had a light clear red color with a green cast, anda viscosity of 599 seconds at 210 F.

Portions of the original condensation product,

and of the product after subjection to the silent electric dischargewere each added to light and heavy waxy oils. .The characteristics ofthe original oil andthe resulting blends are shown in the followingtable:

Light oil Heavy oil Waxy oils:

Viscosity, seconds Saybolt@2l0 F.. 44 70 Viscosity index 100 100 Pourpoint, F 30 30 +04% condensation product:

- Pour point, 4 -l0 +04% voltolized condensation product: Iour point, Fa0 The crude condensation product, prepared as described in the aboveexample, may be subiected after the separation of aluminum chloridesludge and without further finishing, directly to voltolization toproduce similar pour depressants of improved color and increasedeffectiveness. In this'manner ordinary treating and refining losses,which are substantial and may amount to as high as 25% or more,'areavoided.

While' the treatment with silent electric disabove example produced anincrease of about 100% in'the viscosity of the synthetic oil,much-milder treatments at lower voltages,

lower frequencies and/orv for shorter periods of] increase of not over10 time, which produce an the synthetic oil, also as distillates, and

- shown in Example I and a pour point of with the heavy oil shown inExample I. It is I approximately depressants generalm.

serve to refine the oil and to produce substantial improvements in itsappearance and blending characteristics with petroleum lubricants. Thecolor of the oil is substantially improved even by such mild treatmentwith silent electric discharge that the viscosity of the oil isincreased only 1 or 2%. More intensive treatments at higher voltages,frequencies and/or for longer periods of time may=also be used, butthese are not generally desirable when an improved pour point depressantadaptable for use in all waxy oils is desired. It has been observed thatthe effectiveness of the voltolized pour point depressant in waxy oilsof low viscosity is impaired if the voltolization treatment is made toointensive. For example, when the voltolization of the synthetic oildescribed in Example I is continued until the voltolized product has aviscosity of 711 seconds Saybolt at 210 F., (corresponding to anincrease of about 140% in the viscosity of the synthetic oil), a 0.4% ofthis product produces a blend having a pour point of 10 F. with thelight oil F.

thus apparent, that too intensive voltolization results in a pourdepressant which is less effective in certain lubricating oils.

The voltolization of the above example may also be continued so as toproduce an improved cosity several times greater than that of theoriginal 011. For example, the voltolization treatment described inExample I may be continued until a voltolized synthetic product having aviscosity above 1,000 to 2,000 seconds Saybolt at 210 F. is produced.This highly viscous product is also of superior color and is suitablefor use as a blending agent with other lubricating oils, particularlythose derived from petroleum, in order to increase the viscosity andviscosity index of such oils and/ or as an oxidation inhibitor.

The apparatus used in the present process may be of the usual type oftube or trommel design. The tube type of apparatus comprises a verticaltube preferably constructed of a dielectric material such as glasscoated on the outside with a conductor electrode, a central electrodedisposed in 'the center of this tube, provision being made for a hightension silent discharge between the electrodes. The trommel type ofapparatus comprises a series of insulated plates placed a fewmillimeters apart and mounted on a rotatableshait, the entire shaft withits plates being disposed within a horizontal drum maintained half fullof the material to be voltolized. The bottom portions of the plates dipinto the material to be voltolized and as the shaft rotates, thematerial drips down over the surface of the plates forming a thin filmthereon. The high tension silent discharge occurs between the plates. Inapparatus of this type it is generally preferred to operate at apressure below about 20 cm. of mercury and preferably about 2 to 10 cm.and at an electrode potential of about 1,000 to 10,000 volts or more ata frequency of about 500 to 10,000 cycles or more per second.

The treatment with silent electric discharge may be conducted. inthe-presence of hydrogen product having a isthe synthetic oil shown in gor other preferably reducing gases, such as carbon monoxide, natural gasor other hydrocarbon gases or vapors, water gas, coke oven gases and thelike.

' The present invention is applicable to the improvement of-synthetichydrocarbon pourpoint including those prepared by the Friedel-Crafts,Fittig, Wurtz and other types of syntheses. For example, the syntheticpour point depressants described in U. S. Patent No, 1,815,022 grantedJuly 14, 1931, to G. H. B. Davis, and in British Patent No. 349,071accepted May 11, 1931, may be improved bytreatment with silent electricdischarge according to the present invention.

This invention is not to be limited to any examples or explanations, allof which are presented herein solely for purpose of illustration, but islimited only by the following claims, in which it is desired to claimall novelty insofar as the prior art permits.

We claim:

1. Process for improving an unrefined synthetic hydrocarbon pour pointdepressant prepared by chemical condensation from an aliphatic reactanthaving about 10 to carbon atoms in a straight chain to give the pourpoint depressant improved color and potency marked by increasedeffectiveness in lowering the pour point of a wax-com taining oil havinga Saybolt viscosity of seconds at 210 F. which comprises voltolizing thecrude pour point depressant product by the action of silent electricdischarges until the viscosity of the resulting voltolized product isabout higher but less than about higher than the viscosity of said crudepour point depressant product.

2. Process for refining a crude black alkylactant with an aliphaticreactant having a straight chain of 10 to 30 carbon atoms whichcomprises subjecting said crude condensation product to the action ofsilent electric discharges until the thus treated condensation productis given a clear red. color and a green cast with an increase of itsviscosity limited to about 100%.

3. Process for refining a crude black pour point depressant synthesizedby the condensation of chlorinated paraffin wax with an aromatichydrocarbon to make an improvement in the color of the pour pointdepressant and in its effectiveness for lowering the pour point of aheavy waxcontainin oil having a Saybolt viscosity of about 70 seconds at210 R, which comprises voltolizing said crude pour point depressant bythe action of silent electric discharges, and discontinuing thevoltolizing when the increase in viscosity of the voltolized product isabout 100% but less than 140% above that of the crude pour pointdepressant.

JOSHUA A, TILTON. ROGER W. RICHARDSON.

